Abstract: Tainan gas field in Qaidam basin is a typical unconsolidated sandstone reservoir, which is characterized by loose stratum, sandstone interbedded with mudstone, surrounded by edge water and complex gas-water distribution. During the mid-late development period of gas reservoirs, the changes of formation resistivity are not obvious after edge water invasion, resulting in the difficulties of fluid identification in the reservoir. Based on the logging data normalization and logging interpretation technologies for water invasion, the lithology-electrical property relations are used to study water invasion mechanism. The electrical property curves obtained from conventional logging and production logging are used to identify water invasion zones qualitatively, a method to identify water invasion characteristic is proposed on the basis of lithology-electrical property rendezvous, quantitative parameter identification and horizon calibration are performed for water invasion zones, and a set of water invasion evaluation technologies has been established and the difficulties of water invasion identification in low-resistivity gas zones can be overcome. The established logging interpretation mode and evaluation method for water invasion zones are put into use in some newly-drilled wells and the interpretation coincidence rate is 84.2%, which proves that the lithology-electrical property rendezvous method can be the references for water invasion zone identification and interpretation in other unconsolidated gas reservoirs